The Moon is about to take a bite out of the sun. On Saturday, August 11th, there will be a partial solar eclipse visible from locations around the Arctic Circle and across much of Asia. During the 3+ hour event, as much as 73% of the solar disk will be covered. Selected cities in the eclipse zone include Moscow (2.1% coverage), Oslo (4.8%), Raykjavik (20%), Tromso (29%), and Seoul (35%).    www.spaceweather.com

An interplanetary shock wave hit Earth's magnetic field on April 19th around 23:50 UT. When the disturbance arrived, the density of solar wind flowing around our planet abruptly quadrupled and a crack opened in Earth's magnetic field. The resulting G2-class geomagnetic storm sparked unusual "electric blue" auroras. 

"I've been flying airplanes for 20 years and photographing aurora for 10 years, but I've never seen anything like this before" reports pilot Matt Melnyk, who photographed the display from 39,000 feet.  "Electric blue auroras!" he says. "This was while on a red eye flight from Edmonton to Toronto around 4 am over northern Manitoba. Unbelievable sky. I was able to grab some hasty shots with a cell phone."

Auroras are usually green--a sign of oxygen. Rare blue auroras are caused by nitrogen molecules. Energetic particles striking N2+ at the upper limits of Earth's atmosphere can produce an azure glow during intense geomagnetic storms. 

What is an interplanetary shock wave? It is a supersonic disturbance in the gaseous material of the solar wind. These waves are usually delivered by coronal mass ejections (CMEs). Indeed, this one might have been a minor CME that left the sun unrecognized earlier this week.

Alternately, it might have been an unusually sharp co-rotating interaction region (CIR). CIRs are transition zones between slow- and fast-moving streams of solar wind. They contain plasma density gradients and magnetic fields that often do a good job sparking auroras.
www.spaceweather.com

See also: 'Strong New Moon, Solar Activity and Gateways Ahead' by Sandra Walter, Wayshower, Ascension Guide and Gatekeeper

A strong geomagnetic storm was brewing in the skies above Alberta, Canada, on Sept. 27th when photographer Alan Dyer looked up and saw a ribbon of purple light arcing cross the sky. It was the mysterious aurora known as "Steve": 

"The Steve arc appeared for only about 20 minutes, starting at 10:45 pm MDT, during a lull in the main display," says Dyer, who captured the arc in a 6-shot, 360o panorama.For many years, northern sky watchers have reported this luminous form occasionally dancing among regular auroras. It was widely called a "proton arc" until researchers pointed out that protons probably had nothing to do with it. So members of the Alberta Aurora Chasers group gave it a new name: "Steve."
"We seem to be ideally located in the Canadian Prairies for sighting Steve, as we often get the main aurora to our north, placing Steve overhead or to our south," notes Dyer.

No one fully understands the underlying physics of the purple ribbon. One of the European Space Agency's Swarm satellites flew straight through Steve during a previous apparition. Data revealed a relatively hot river of gas, about 25 km wide, flowing rapidly through Earth's outer atmosphere. "Steve seems to be a thermal emission from hot flowing gas rather than from precipitating electrons," says Dyer, "but his origin and nature are still mysterious."  www.spaceweather.com

GEOMAGNETIC STORM PREDICTED: NOAA forecasters say there is a 75% chance of moderately strong (G2-class) geomagnetic storms on Sept. 13th. That's when a CME hurled into space by a powerful X8-class solar flare on 10 September will likely deliver a glancing blow to Earth's magnetic field. The impact of the CME could be enhanced by a fast-moving solar wind stream, expected to arrive at about the same time. If the G2-storm materializes, auroras in the USA could appear as low as New York to Wisconsin to Washington state.

SOLAR RADIATION STORM AND GROUND LEVEL EVENT: On Sept. 10th, departing sunspot AR2673 erupted, producing a powerful X8-class solar flare. The explosion propelled a CME into space and accelerated a swarm of energetic protons toward Earth. Both are visible in this coronagraph movie from the Solar and Heliospheric Observatory (SOHO):

The many specks in this movie are not stars--they are solar protons striking SOHO's digital camera. Almost two days later these protons are still streaming past our planet, causing a moderately strong (S2-class) solar radiation storm. The latest data from SOHO show an ongoing blizzard of digital "snow" in coronagraph images:

What made this flare so 'radioactive'? It has to do with the location of AR2673 at the time of the explosion. The sun's western limb is magnetically well-connected to Earth. Look at this diagram. Magnetic fields spiraling back from the blast site led directly to our planet, funneling these energetic protons Earthward.

Normally, solar radiation storms are held at bay by our planet's magnetic field and upper atmosphere. On Sept.10th, however, there was a "ground level event" (GLE). Neutron monitors in the Arctic, Antarctic, and several other high latitude locations detected a surge of particles reaching all the way down to Earth's surface:

"In historical terms, this was a relatively small ground level event-- only about one thousandth as strong as the event of 23 Feb 1956, which is the largest measured," says Clive Dyer, a Visiting Professor at the University of Surrey Space Centre.

However, that does not mean the Sept.10th GLE was negligible. Dyer says that "passengers flying on high-latitude routes at 40,000 feet could have absorbed an extra 10 microSieverts of radiation. During the first hour of the GLE, the dose rate inside the aircraft during such a flight would have approximately doubled."

He also notes that the GLE could have caused minor upsets of onboard electronics and avionics, although nothing on the scale of the epic 1956 GLE, "which would be very challenging to modern systems."

"Since measurements began around 1942 there have now been 73 events detected by ground level radiation monitors," Dyer adds. "The Sept.10, 2017, event is far from the strongest, but it is of special interest because it demonstrates the need for continual vigilance even during Solar Minimum."      www.spaceweather.com

On Sept. 6th at 12.02 UT, sunspot AR2673 unleashed a major X9.3-class solar flare--the strongest solar flare in more than a decade. X-rays and UV radiation from the blast ionized the top of Earth's atmosphere, causing a strong shortwave radio blackout over Europe, Africa and the Atlantic Ocean (blackout map). The explosion also produced a CME, shown here in a movie from NASA's STEREO-A spacecraft. (The fast moving star-like object in the STEREO-A movie is the planet Mercury.) NOAA analysts are still modeling the trajectory of the CME to determine whether or not it is Earth-directed.

Many readers are asking about the historic context of this event. How epic is it? Answer: This is a decade-class flare. A list of the most powerful solar flares recorded since 1976 ranks today's flare at #14, tied with a similar explosion in 1990. Compared to the iconic Carrington Event of 1859, or even the more recent Halloween storms of 2003, this event is relatively mild. Modern power grids, telecommunications, and other sun sensitive technologies should weather the storm with little difficulty.

On the other hand, sky watchers could see some fantastic auroras before the week is over. And ham radio operators will surely be noticing strange propagation effects as the sun exerts its influence on our planet's ionosphere.Stay tuned for updates.

The source of today's major flare is huge sunspot AR2673, shown here in a Sept. 5th photo taken by amateur astronomer Philippe Tosi of Nîmes, France:

How big is AR2673? An image of Earth has been inserted for scale. The largest of AR2673's dark cores are as wide as our entire planet, and they are surrounded by dozens of smaller cores as big as continents. Amateur astronomers with safely-filtered solar telescopes will have no trouble seeing this behemoth.  Overarching the complex collection of spots is a tangled magnetic canopy that harbors energy for strong solar flares. Stay tuned for more explosions...
www.spaceweather.com

Only a few weeks ago, it seemed that the sun would be quiet and featureless when the Moon eclipsed it on Aug. 21st. Solar Minimum was in full swing. This weekend, however, the sun is welcoming the eclipse with a burst of renewed activity. "As the Moon approaches the sun, our nearest star is extending a friendly hand towards it," says Dave Eagle  who sends this picture from Higham Ferrers, England:

"There is a huge prominence on the sun's eastern limb. If you are in the total eclipse path set your clock to greet this awesome spectacle on Monday," he says.

And that's just for starters. In addition, a remarkably-long sunspot group is sprawling across the solar disk. AR2671 stretches 140,000 miles from end to end, almost twice as wide as the planet Jupiter. Bill Hrudey sends this picture of the behemoth from the Cayman Islands:

Amateur astronomers watching the eclipse through safe solar telescopes will have no trouble seeing the rugged edge of the Moon cut across this impressive sunspot, eclipsing one dark core after another.  If we're really lucky, the sunspot will explode. AR2671 has a 'beta-gamma' magnetic field that harbors energy for M-class solar flares. Free: Solar Flare Alerts
www.spaceweather.com

On Aug. 21, 2017, every square inch of the USA will experience a solar eclipse.  In most places, the eclipse will be partial - that is, the Moon will cross the sun off-center, leaving a crescent shaped portion of the solar disk exposed. Is it really worth the trip to the path of totality when you can stay home and see the partial eclipse?  Pulitzer prize winner Annie Dillard, who witnessed both types of eclipses in 1979, compared them as follows:

"A partial eclipse is very interesting. It bears almost no relation to a total eclipse. Seeing a partial eclipse bears the same relation to seeing a total eclipse as kissing a man does to marrying him, or as flying in an airplane does to falling out of an airplane."

Indeed, during the minutes of totality, the whole world changes.  Saying that day turns into night barely scratches the surface of it. The shadow of the Moon lances down to Earth from a quarter million miles away. On one end is you; on the other end is a million square miles of dusty lunar terrain. You're connected, and you can feel the cold.

Darkness inside the path of totality has an alien quality. Because the shadow is only 70 miles wide, you can see daylight at the edges even while you stand in the dark core. This distant scattered light produces a slight reddish glow and unusual shadow effects. Many birds stop singing, daytime flower blossoms begin to close as if for the night, and bees return to their hives.

"What you see in an eclipse is entirely different from what you know," says Dillard, whose brilliant essay "Total Eclipse" is a must-read for anyone deciding whether to stay home ... or have their minds blown.
www.spaceweather.com

What do Christmas Eve, Christmas, and Boxing Day 2016 have in common? They were days without sunspots. Throughout the holiday weekend, the face of the sun was completely blank, and the sun itself looked like a big orange Christmas ornament:

Including Dec. 24th, 25th and 26th, 2016 has had 31 'spotless days'--a whole month's worth.  We haven't had this many blank suns in a single year since 2010 (51 days).  This is a sign that the sunspot cycle is crashing toward a new Solar Minimum.

There are many misconceptions about Solar Minimum. One holds that auroras vanish when sunspots disappear. Christmas Day 2016 was proof that the opposite is true. Without a hint of a sunspot on the solar disk, intense auroras raged around the Arctic Circle on Dec. 25th. What caused the luminous outburst? An enormous hole in the sun's atmosphere directed a stream of solar wind toward Earth, sparking a week-long display that is still underway. Such atmospheric holes are common during Solar Minimum, which is a fine time to see Arctic auroras.

Many people think space weather becomes dull or stops altogether during Solar Minimum. In fact, space weather changes in interesting ways. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth; galactic cosmic rays penetrate our atmosphere with relative ease. Yes, Solar Minimum is coming ... but it won't be dull.
www.spaceweather.com

Six days after Earth entered a stream of high-speed solar wind ... we're still inside. The solar wind continues to blow faster than 500 km/s on Oct. 31st. Although it is not as gusty as it was during first contact on Oct. 25th, the relentless pressure of the sun's electrically charged wind on Earth's magnetic field is causing the poles to glow with beautiful auroras. Marketa S. Murray sends this picture from Fairbanks, Alaska, on Oct. 29th:

"When you stand there and the whole sky is just dancing overhead, your adrenaline and endorphin get so high," says Murray. "It's mind blowing every time it happens. It never gets old, even for an Alaskan!"

Until Earth fully exits this stream, polar auroras remain likely. A good way to follow the action is to tune into a live webcam in Sweden's Abisko National Park. "We have seen the lights nearly every night in October!" says Chad Blakley of Lights over Lapland, who operates the camera.
Watch it now.    www.spaceweather.com

Something interesting is happening on the sun. On June 3rd the sunspot number dropped to 0, and the solar disk is still blank on June 5th. Latest images from NASA's Solar Dynamics Observatory reveal no significant dark cores:

What does this mean? The solar cycle is like a pendulum, swinging back and forth between periods of high and low sunspot number every 11 years. Today's blank sun is a sign that the pendulum is swinging toward low sunspot numbers. In other words, Solar Minimum is coming.
The spotless state of today's sun is just temporary. Underneath the visible surface of the sun, the solar dynamo is still churning out knots of magnetism that will soon bob to the surface to make new sunspots. The current solar cycle is not finished. It is, however, rapidly waning.

Forecasters expect the next Solar Minimum to arrive in 2019-2020. Between now and then, there will be lots of spotless suns. At first, the blank stretches will be measured in days; later in weeks and months. Don't expect space weather to grow quiet, however. Solar Minimum brings many interesting changes. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth. Galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, a cosmic ray surge is already underway. Goodbye sunspots, hello deep-space radiation!
www.spaceweather.com

Anyone wondering why the sun has been so quiet lately? The reason is shown in the graph below. The 11-year sunspot cycle is crashing:

For the past two years, the sunspot number has been dropping as the sun transitions from Solar Max to Solar Min. Fewer sunspots means there are fewer solar flares and coronal mass ejections (CMEs). As the explosions subside, we deem the sun "quiet."

But how quiet is it, really? A widely-held misconception is that space weather stalls and becomes uninteresting during periods of low sunspot number. In fact, by turning the solar cycle sideways, we see that Solar Minimum brings many interesting changes. For instance, the upper atmosphere of Earth collapses, allowing space junk to accumulate around our planet. The heliosphere shrinks, bringing interstellar space closer to Earth. And galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, a cosmic ray surge is already underway. (Bringing higher vibrational energy.  Messenger Spirit)
www.spaceweather.com

An annual pilgrimage by amateur and professional photographers to Yosemite National Park to capture a unique solar lighting effect has been revived with the recent wet weather.

For a couple of weeks in February, Yosemite's Horsetail Fall gets bathed in the light of the setting sun, creating what is known as a "firefall," with the waterfall and wet rockface creating an orange glow from the reflection.  In recent years, a lack of water or cloudy weather has meant the spectacular effect does not appear during the brief window when the sun is aligned perfectly on the fall. This year, images of the firefall at Horsetail Fall has blanketed social media.

The history of the Yosemite Firefall began with a manmade firefall in the last 19th century, when a campfire at the top of Glacier Point was pushed over the edge of the cliff, treating spectators below to a fiery spectacle. It became an annual event that increased in size and popularity, until it was finally discontinued in 1968.

In 1973, close to the 100-year anniversary of the first Yosemite Firefall, a photographer captured the first known photo of the natural firefall at Horsetail Fall.

Carlos E. Castañeda is Senior Editor, News & Social Media for CBS San Francisco and a San Francisco native

Charles Q. Choi : IEEE Spectrum : 14 Dec 2015

Solar heat could help generate both electricity and hydrogen fuel at the same time in a system that scientists in Switzerland and the United States call "hydricity." Such a system could supply electricity round-the-clock with an overall efficiency better than many photovoltaic cells, researchers add.

There are two ways solar energy is used to generate electricity. Photovoltaic cells directly convert sunlight to electricity, while solar thermal power plants—also known as concentrating solar power systems—focus sunlight with mirrors, heating water and producing high-pressure steam that drives turbines.

Photovoltaic cells only absorb a portion of the solar spectrum, but they can generate electricity from both direct and diffuse sunlight. Solar thermal power plants can use more wavelengths of the solar spectrum, but they can only operate in direct sunlight, limiting them to sun-rich areas. Moreover, the highest conversion efficiencies reported yet for solar thermal power plants are significantly less than those for photovoltaic cells.

Scientists now suggest that coupling solar thermal power plants with hydrogen fuel production facilities could result in "hydricity" systems competitive with photovoltaic designs.

Today's solar thermal power plants operate at temperatures of up to roughly 625 degrees C. However, the researchers noted that solar thermal power plants are more efficient at higher temperatures. What's more, when they reach temperatures above 725 degrees C they can split water into it's constituents, hydrogen and oxygen.

An integrated "hydricity" system would produce both steam for generating electricity and hydrogen for storing energy. And each makes the other more efficient. Set to produce hydrogen alone, its production efficiency approaches 50 percent, the researchers claim. This is because the high-pressure steam the system generates can easily be used to pressurize hydrogen. The substantial amount of power needed to compress hydrogen fuel for later transport and use is often neglected when it comes to calculating hydrogen production efficiency.

Furthermore, this new solar thermal energy design can generate electricity with standalone efficiencies approaching up to an unprecedented 46 percent, researchers say. This is because the high-temperature steam leaving high-pressure turbines can run a succession of lower-pressure turbines, helping make the most of the solar thermal energy the system collects.

Moreover, the hydrogen fuel the system generates can be burned to generate electricity after nightfall, for round-the-clock power. The researchers say the efficiency of this hydrogen-to-electricity system could reach up to 70 percent, comparable to the highest reported hydrogen fuel cell efficiencies.

Altogether, the researchers say the sun-to-electricity efficiency of hydricity, averaged over a 24-hour cycle, might approach roughly 35 percent, nearly the efficiency attained using the best multijunction photovoltaic cells combined with batteries. In addition, they note that the hydrogen fuel the system produces could find use in transportation, chemical production, and other industries. Finally, unlike batteries, stored hydrogen neither discharges over time nor degrades with repeated use.

The scientists at Purdue University in West Lafayette, Ind., and the Federal Polytechnic School of Lausanne in Switzerland detailed their findings online 14 December in the journal Proceedings of the National Academy of Sciences.

For the past week, solar activity has been low. However, the sun has not been quiet. "I have noted that the sun has been extremely dynamic at shortwave radio wavelengths with almost constant Type III bursting," reports Thomas Ashcraft of New Mexico. He has been hearing loud bursts of static coming from the loudspeaker of his amateur radio telescope whenever he points it at the sun. Click here to hear a sample:

Type III solar radio bursts are caused by solar flares. Electrons accelerated by strong flares race through the sun's atmosphere, causing a ripple of plasma waves and radio static. Yet, ironically, there have been no strong solar flares. Nevertheless, suggests Ashcraft, "all of the bursting indicates a lot of magnetic complexity and movement in the sunspots."

The biggest sunspot of all, AR2396, is about to rotate off the western edge of the sun. After it departs, the static might subside. Until then, shortwave radio operators should remain alert for solar bursts. The sun is not so quiet, after all.
www.spaceweather.com